Emulsion Composition

ABSTRACT

The present invention provides an emulsion composition containing (a) a first phase with (i) an oil soluble inert medium; and (ii) an emulsifier capable of forming a water-in-oil emulsion; and (b) a second phase with (i) a metal base; (ii) an aqueous medium; and (iii) optionally a compound containing two or more hydroxyl groups, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil. The invention further provides a method of preparing the emulsion composition and its use in a marine engine.

CROSS REFERENCE

This application claims priority from U.S. Patent Application Ser. No. 60/643,681 filed on Jan. 13, 2005.

FIELD OF INVENTION

The present invention relates to an emulsion composition containing an inert medium, a metal base, an emulsifier, an aqueous base and optionally a compound containing 2 or more hydroxyl groups. The invention further discloses the use of an emulsion composition in an internal combustion engine.

BACKGROUND OF THE INVENTION

A variety of lubricant oils are available having various total base numbers. One reason for having a total base number above zero in a lubricant is that acidic products are more likely to cause corrosion and wear to metal parts of a device than bases, which tend not to be involved in corrosion. Thus, lubricants are formulated with sufficient excess base that over their intended lifetime, they remain neutral or slightly basic.

One particular use of a lubricant with a high total base number is in marine diesel applications which economically burn residual fuels with a sulphur content up to about 4.5 weight percent. Due to the high amount of sulphur containing species in the economical residual fuel, the combustion products include high amount of acidic SO_(x) which causes additional wear to the cylinder wall and the rings of the piston. A solution to this lubrication/corrosion problem caused by the SO_(x) is to include excess base in the lubricant oil so that the SO_(x) is converted to a metal salt of the acid, which has less tendency to cause corrosion or wear. In many marine diesel applications, the cylinder oil is injected near the rings of the piston on a continual basis to provide both continued lubrication and replace the base lost to neutralisation. In these applications, the cylinder lubricant is continuously consumed rather than returned to a sump. The marine diesel lubricant also needs cleanliness, spreadability, corrosive wear resistance and filterability.

PCT Application 03/044138 A2 (Cook et al.) discloses a lubricant composition containing (a) at least one emulsifier capable of forming a water in oil emulsion, (b) a non-borated base that at least 1 TBN to said lubricant and at least 10 wt. % of the base is insoluble in the oil insoluble solvent. The base contains a metal selected from potassium, sodium, calcium, magnesium, lithium or aluminum and a counter-ion selected from a hydroxide, a carbonate, a bicarbonate, a C₁-C₅ organic acid; an oxide; ammonia; an amine, a guanidine carbonate, urea; or other organic nitrogen compound which generates ammonia on ignition, or combinations thereof.

U.S. Pat. No. 6,533,829 discloses a stabilised liquid hydrocarbon fuel composition containing an alcohol with 5 to 10 carbon atoms, a carboxylic amide containing 5 to 10 carbon atoms present at 0.5 to 3 parts by weight relative to the amount of alcohol; and a carboxylic acid containing 5 to 10 carbon atoms present at 3 to 10 parts by weight relative to the amount of alcohol.

U.S. Pat. No. 6,533,830 discloses a fuel or lubricant composition containing a polyalkyene alcohol polyalkoxylate.

It would be desirable to have an emulsion composition with at least one property from acceptable cleanliness, acceptable spreadability, acceptable corrosive wear resistance and acceptable/improved filterability. The present invention provides an emulsion composition with at least one property from acceptable cleanliness, acceptable spreadability, acceptable corrosive wear resistance and acceptable/improved filterability.

SUMMARY OF THE INVENTION

The present invention provides an emulsion composition comprising: (a) a first phase comprising: (i) an oil soluble inert medium; and (ii) an emulsifier capable of forming a water-in-oil emulsion; and (b) a second phase comprises: (i) a metal base; (ii) an aqueous medium; and (iii) optionally a compound containing two or more hydroxyl groups, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.

In one embodiment, the emulsion composition comprises: (a) a first phase comprising: (i) an oil soluble inert medium; and (ii) an emulsifier capable of forming a water-in-oil emulsion; and (b) a second phase comprises: (i) a metal base; (ii) an aqueous medium; (iii) a compound containing two or more hydroxyl groups, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention provides an emulsion composition comprising:

(a) a first phase comprising:

-   -   (i) an oil soluble inert medium; and     -   (ii) an emulsifier capable of forming a water-in-oil emulsion;         and

(b) a second phase comprises:

-   -   (i) a metal base;     -   (ii) an aqueous medium; and     -   (iii) optionally a compound containing two or more hydroxyl         groups,         wherein a base in the form of an alkali metal or an alkaline         earth metal oxide, hydroxide, carbonate, bicarbonate; or         combinations thereof; and wherein the emulsion composition has a         flow rate through a 45 μm filter of more than 8 ml/min in a         filterability test carried out at ambient temperature (e.g.         20° C. to 25° C.) and 45 kPa applied vacuum; wherein the filter         has diameter of 5 cm and a mesh size of about 45 μm; and wherein         the oil soluble inert medium in the filtration test is an oil of         lubricating viscosity of a SAE 50 base oil.

In one embodiment, the emulsion composition comprises:

(a) a first phase comprising:

-   -   (i) an oil soluble inert medium; and     -   (ii) an emulsifier capable of forming a water-in-oil emulsion;         and

(b) a second phase comprises:

-   -   (i) a metal base;     -   (ii) an aqueous medium;     -   (iii) a compound containing two or more hydroxyl groups; and         wherein a base in the form of an alkali metal or an alkaline         earth metal oxide, hydroxide, carbonate, bicarbonate; or         combinations thereof; and wherein the emulsion composition has a         flow rate through a 45 μm filter of more than 8 ml/min in a         filterability test carried out at ambient temperature and 45 kPa         applied vacuum; wherein the filter has diameter of 5 cm and a         mesh size of about 45 μm; and wherein the oil soluble inert         medium in the filtration test is an oil of lubricating viscosity         of a SAE 50 base oil.

In several embodiments, the emulsion composition has a flow rate through a 45 μm filter of 9 ml/min or more in the filterability test, 10 ml/min or more in the filterability test or 11 ml/min or more in the filterability test. Examples of ranges of suitable flow rate include 8.5 ml/min to 50 ml/min, 9.5 ml/min to 40 ml/min or 10.5 ml/min to 30 ml/min.

In one embodiment, the filterability test has a second phase of the emulsion composition containing a solids content of a metal base from 15 wt % to 25 wt %.

In one embodiment, the filterability test as described above is replaced by measuring the Theological properties of the metal base during dewatering. The Theological properties are measured using a Bohlin Instruments Gemini™ Rheometer. The methodology of the test is described in the Example section and the results obtained are the length of time required for the formation of a filter cake. Generally, a filter cake forms when the metal base aggregates. The methodology of the Bohlin Instruments Gemini™ Rheometer required the metal base to be suspended in water rather than in the emulsion composition. Generally, the Gemini™ Rheometer is operated at ambient temperature.

In several embodiments, the length of time required for the metal base to form of a filter cake is at least 60 seconds (s), or at least 65 s or at least 70 s. Examples of ranges time required for the formation of a filter cake include 62 s to 150 s, or 68 s to 130 s or 75 s to 110 s.

In several embodiments, the emulsion composition is a water in oil composition with a wt % ratio of the first phase relative to the second phase of at least 51 to 49, or at least 55 to 45, or at least 60 to 40, or at least 65 to 35 or at least 70 to 30.

The emulsion composition when employed in an internal combustion engine in several embodiments has a total base number (TBN) of at least 1, at least 5, at least 10 or at least 30 mg KOH/g.

The emulsion composition when employed in a marine diesel combustion engine in several embodiments has a total base number (TBN) of at least 5, at least 10, at least 20 or at least 30.

The First Phase Oil Soluble Inert Medium

The first phase of the invention includes an oil soluble inert medium. The oil soluble inert medium includes a liquid fuel or an oil of lubricating viscosity.

The inert oil medium is present in several embodiments from 40 wt % to 99.9 wt %, or from 50 wt % to 97 wt %, or from 55 wt % to 95 wt %, or from 60 wt % to 90 wt % of the emulsion composition.

Oil of Lubricating Viscosity

In one embodiment, the emulsion composition includes natural or synthetic oils of lubricating viscosity, oil derived from hydrocracking, hydrogenation, hydrofinishing, unrefined, refined and re-refined oils or mixtures thereof. In several embodiments, the oil of lubricating viscosity has a SAE grade of 20-70, 30-50 or 40-60.

Natural oils include animal oils, vegetable oils, mineral oils or mixtures thereof. Synthetic oils include a hydrocarbon oil, a silicon-based oil, a liquid esters of phosphorus-containing acid. Synthetic oils may be produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes.

Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. In several embodiments the oil of lubricating viscosity comprises an API Group I, II, III, IV, V, VI or mixtures thereof, or an API Group I, II, III or mixtures thereof. If the oil of lubricating viscosity is an API Group II, III, IV, V or VI oil there may be up to 40 wt % or up to a maximum of 5 wt % of the lubricating oil an API Group I oil.

Liquid Fuel

In one embodiment, the emulsion composition includes a liquid fuel that is normally a liquid at ambient conditions. The liquid fuel includes a hydrocarbon fuel, a nonhydrocarbon fuel, or a mixture thereof. The hydrocarbon fuel may be a petroleum distillate including a gasoline as defined by ASTM (American Society for Testing and Materials) specification D4814 or a diesel fuel as defined by ASTM specification D975.

In one embodiment, the liquid fuel is a gasoline, and in another embodiment, the liquid fuel is a gasohol (i.e., gasoline alcohol mixture), and in another embodiment the liquid fuel is a diesel fuel. The hydrocarbon fuel includes a hydrocarbon prepared by a gas to liquid process, for example, Fischer-Tropsch. The nonhydrocarbon fuel includes an oxygen containing composition, often referred to as an oxygenate. The nonhydrocarbon fuel includes a monohydric alcohol, an ether, a ketone, an ester of a carboxylic acid, a nitroalkane, or a mixture thereof. Examples of the nonhydrocarbon fuel include methanol, ethanol, methyl t-butyl ether, methyl ethyl ketone, transesterified oils and/or fats from plants and animals such as rapeseed methyl ester and soybean methyl ester, and nitromethane. Examples of mixtures of the hydrocarbon and the nonhydrocarbon fuel include gasoline and methanol and/or ethanol, diesel fuel and ethanol, and diesel fuel and a transesterified plant oil such as rapeseed methyl ester.

Emulsifier

The first phase includes an emulsifier capable of forming a water-in-oil emulsion or mixtures thereof. The emulsifier is present in one embodiment from 0.01 wt % to 20 wt %, in another embodiment from 0.05 wt % to 10 wt %, in another embodiment 0.1 wt % to 5 wt % and in another embodiment from 0.2 wt % to 3 wt % of the emulsion composition.

The emulsifier includes a hydrocarbon lubricant-soluble hydrocarbyl substituted carboxylic acid acylating agent. The hydrocarbyl substituted carboxylic acid acylating agent emulsifier may be produced by reacting a hydrocarbyl substituted carboxylic acid acylating agent with ammonia or an amine, the hydrocarbyl substituent of said acylating agent having 50 to 500 carbon atoms; (ii) an ionic or a nonionic compound having a hydrophilic lipophilic balance (HLB) of 1 to 30 in another embodiment less than 10, in another embodiment 1 to 8, and in yet another embodiment 2.5 to 6. Those skilled in the art will appreciate that combinations of surfactants may be used with individual HLB values outside of the given ranges provided that the composition of the final emulsifier blend is within these ranges.

The hydrocarbyl-substituted carboxylic acid acylating agent for the hydrocarbon lubricant-soluble product (i) may be a carboxylic acid or a reactive equivalent of such acid. The reactive equivalent may be an acid halide, anhydride, or ester, including partial esters and the like. The hydrocarbyl substituent for the carboxylic acid acylating agent may contain from 50 to 300 or 500 carbon atoms, and in another embodiment 60 to 200 carbon atoms. In one embodiment, the hydrocarbyl substituent of the acylating agent has a number average molecular weight of 500 or 750 to 3000, and in another embodiment 900 to 2000 or 2300.

In one embodiment, the hydrocarbyl-substituted carboxylic acid acylating agent for the hydrocarbon lubricant-soluble product (i) may be made by reacting one or more alpha-beta olefinically unsaturated carboxylic acid reagents containing 2 to 20 carbon atoms, exclusive of the carboxyl groups, with one or more olefin polymers as described more fully hereinafter. The alpha-beta olefinically unsaturated carboxylic acid reagents may be either monobasic or polybasic in nature.

The olefin monomers from which the olefin polymers may be derived are polymerisable olefin monomers characterized by having one or more ethylenically unsaturated groups and they (monomers and polymers).

In one embodiment, the olefin polymer is a polyisobutene group (or polyisobutylene group) having a number average molecular weight of 750 to 3000, and in another embodiment 900 to 2000.

In one embodiment, the acylating agent for the hydrocarbon lubricant-soluble product (i) is a hydrocarbyl-substituted succinic acid or anhydride. The production of these hydrocarbyl-substituted succinic acids or anhydrides via alkylation of maleic acid or anhydride or its derivatives with a halohydrocarbon or via reaction of maleic acid or anhydride with an olefin polymer having a terminal double bond is well known and need not be discussed in detail herein.

In one embodiment, the hydrocarbyl-substituted carboxylic acid acylating agent for the product hydrocarbon lubricant-soluble product (i) is a hydrocarbyl-substituted succinic acylating agent consisting of hydrocarbyl substituent groups and succinic groups. The hydrocarbyl substituent groups are derived from an olefin polymer as discussed above. The hydrocarbyl-substituted carboxylic acid acylating agent is characterized by the presence within its structure of an average of at least 1.3 succinic groups, and in another embodiment from 1.5 to 2.5, and in another embodiment form 1.7 to 2.1 succinic groups for each equivalent weight of the hydrocarbyl substituent. In one embodiment, the hydrocarbyl-substituted carboxylic acid acylating agent is characterized by the presence within its structure of 1.0 to 1.3, and in another embodiment from 1.0 to 1.2, and in another embodiment from 1.0 to 1.1 succinic groups for each equivalent weight of the hydrocarbyl substituent.

In one embodiment, the hydrocarbyl-substituted carboxylic acid acylating agent is a polyisobutene-substituted succinic anhydride, the polyisobutene substituent having a number average molecular weight of 1500 to 3000, and in another embodiment 1800 to 2300, said first polyisobutene-substituted succinic anhydride being characterized by 1.3 to 2.5, and in another embodiment 1.7 to 2.1 succinic groups per equivalent weight of the polyisobutene substituent.

In one embodiment, the hydrocarbyl-substituted carboxylic acid acylating agent is a polyisobutene-substituted succinic anhydride, the polyisobutene substituent having a number average molecular weight of 700 to 1300, and in another embodiment 800 to 1000, said polyisobutene-substituted succinic anhydride being characterized by 1.0 to 1.3, and in another embodiment 1.0 to 1.2 succinic groups per equivalent weight of the polyisobutene substituent.

The hydrocarbon lubricant-soluble product (i) may be formed using ammonia and/or an amine. The amines useful for reacting with the acylating agent to form the product (i) include monoamines, polyamines, and mixtures thereof.

The hydrocarbon lubricant-soluble product (i) may be a salt, an ester, an amide, an imide, or a combination thereof. The salt may be an internal salt involving residues of a molecule of the acylating agent and the ammonia or amine wherein one of the carboxyl groups becomes ionically bound to a nitrogen atom within the same group; or it may be an external salt wherein the ionic salt group is formed with a nitrogen atom that is not part of the same molecule. In one embodiment, the amine is a hydroxyamine, the hydrocarbyl-substituted carboxylic acid acylating agent is a hydrocarbyl-substituted succinic anhydride, and the resulting hydrocarbon lubricant-soluble product (i) is a half ester and half salt, i.e., an ester/salt.

In one embodiment, the lubricant soluble product (i) comprises: (i)(a) a first hydrocarbyl-substituted carboxylic acid acylating agent, the hydrocarbyl substituent of said first acylating agent having 50 to 500 carbon atoms; and (i)(b) a second hydrocarbyl-substituted carboxylic acid acylating agent, the hydrocarbyl substituent of said second acylating agent having 50 to 500 carbon atoms, said first acylating agent and said second acylating agent being the same or different; said first acylating agent and said second acylating agent being coupled together by a linking group derived from a compound having two or more primary amino groups, two or more secondary amino groups, at least one primary amino group and at least one secondary amino group, at least two hydroxyl groups, or at least one primary or secondary amino group and at least one hydroxyl group; said coupled acylating agents being reacted with ammonia or an amine. The molecular weight of the hydrocarbyl substituent for the first acylating agent may be the same as or it may be different than the molecular weight of the hydrocarbyl substituent for the second acylating agent.

In one embodiment, the number average molecular weight for the hydrocarbyl substituent for the first and/or second acylating agent is in the range of 1500 to 3000, and in another embodiment 1800 to 2300.

In one embodiment, the number average molecular weight for the hydrocarbyl substituent for the first and/or second acylating agent is in the range of 700 to 1300, and in another embodiment 800 to 1000. The first and/or second hydrocarbyl-substituted carboxylic acid acylating agent may be a polyisobutene-substituted succinic anhydride, the polyisobutene substituent having a number average molecular weight of 1500 to 3000, and in another embodiment 1800 to 2300. This first and/or second polyisobutene-substituted succinic anhydride may be characterized by at least 1.3, in another embodiment 1.3 to 2.5, and in another embodiment 1.7 to 2.1 succinic groups per equivalent weight of the polyisobutene substituent. The first and/or second hydrocarbyl-substituted carboxylic acid acylating agent may be a polyisobutene-substituted succinic anhydride, the polyisobutene substituent having a number average molecular weight of 700 to 1300, and in another embodiment 800 to 1000. This first and/or second polyisobutene-substituted succinic anhydride may be characterized by 1.0 to 1.3, and in another embodiment 1.0 to 1.2 succinic groups per equivalent weight of the polyisobutene substituent. The linking group may be derived from any of the amines or hydroxamines discussed above having two or more primary amino groups, two or more secondary amino groups, at least one primary amino group and at least one secondary amino group, or at least one primary or secondary amino group and at least one hydroxyl group. The linking group may also be derived from a polyol.

The ratio of reactants utilized in the preparation of these linked products may be varied over a wide range. Generally, for each equivalent of each of the first and second acylating agents, at least one equivalent of the linking compound is used. The upper limit of linking compound is two equivalents of linking compound for each equivalent of the first and second acylating agents. Generally the ratio of equivalents of the first acylating agent to the second acylating agent is 4:1 to 1:4, and in another embodiment 1.5:1.

The first and second acylating agents may be reacted with the linking compound according to conventional ester and/or amide-forming techniques. This normally involves heating acylating agents with the linking compound, optionally in the presence of a normally liquid, substantially inert, organic liquid solvent/diluent. The reaction between the linked acylating agents and the ammonia or amine may be carried out under salt, ester/salt, amide or imide forming conditions using conventional techniques.

The ionic or nonionic compound (ii) has a hydrophilic lipophilic balance (HLB) in the range of 1 to 20 or 30, and in another embodiment 4 to 15 or 20. Examples of these compounds are disclosed in McCutcheon's Emulsifiers and Detergents, 1998, North American & International Edition. Pages 1-235 of the North American Edition and pages 1-199 of the International Edition are incorporated herein by reference for their disclosure of such ionic and nonionic compounds having an HLB in the range of 1 to 10 or 30. In one embodiment, the ionic or nonionic compound (ii) is a poly(oxyalkene) compound. These include copolymers of ethylene oxide and propylene oxide. In one embodiment, the ionic or nonionic compound (ii) is a hydrocarbon lubricant-soluble product made by reacting an acylating agent having 12 to 30 carbon atoms with ammonia or an amine. The acylating agent may contain 12 to 24 carbon atoms, and in another embodiment 12 to 18 carbon atoms. The amine may be any of the amines described above as being useful in making the hydrocarbon lubricant-soluble product (i). The product of the reaction between the acylating agent and the ammonia or amine may be a salt, an ester, an amide, an imide, or a combination thereof.

In one embodiment, the ionic or nonionic compound (ii) is an ester/salt made by reacting hexadecyl succinic anhydride with dimethylethanolamine in an equivalent ratio (i.e., carbonyl to amine ratio) of 1:1 to 1:1.5, and in another embodiment 1:1.35.

In one embodiment, the ionic or nonionic compound can be the reaction product of a copolymer of an alpha olefin of 3 to 25 carbon atoms with maleic anhydride reacted with an amine (as previously described). One such reaction product would be a copolymer of octadecene with maleic anhydride that is reacted with triethylenetetramine or dimethylaminopropylamine. It may be desirable to control crosslinking with these multifunctional reactants by having large amounts of carboxylic acids of lower functionality and/or amines of lower functionality present to avoid forming an insoluble product.

The Second Phase

The second phase comprises a metal base, an aqueous medium and optionally a compound containing two or more hydroxyl groups.

Metal Base

In several embodiments, the metal base in the form of an alkali or alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof. Examples of the metal base include calcium oxide, calcium hydroxide, calcium carbonate, calcium bicarbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate or magnesium bicarbonate. In one embodiment, the metal base is a calcium base and in another embodiment a magnesium base. The metal base may be prepared in a laboratory, commercially quarried or mixtures thereof.

In several embodiments, the total surface area of the metal base as determined by nitrogen BET methods known in the art include 60 m²g⁻¹ or less, 50 m²g⁻¹ or less or 40 m²g⁻¹ or less. Examples of ranges for the total surface area of the metal base include 0.1 m²g⁻¹ to 20 m²g⁻¹, 1 m²g⁻¹ to 15 m²g⁻¹ or 2 m²g⁻¹ to 10 m²g⁻¹.

In several embodiments, the metal base mean particle size as determined after cooling by Coulter® LS230 Particle Size Analyser include 0.01 μm to 50 μm, 0.1 μm to 30 μm, 0.15 μm to 20 μm or 0.2 μm to 10 μm.

In several embodiments, the metal base Zeta Potential includes 0.1 mV to 100 mV, 1 mV to 75 mV or 2 mV to 20 mV.

A person skilled in the art will appreciate that the relationship between zeta potential, mean particle size and total surface area is a complex relationship. Consequently, a suitable metal base may have at least one or two of said characteristics outside the scope of the ranges disclosed above provided that an emulsion composition formed using said metal base has a filterability of more than 8 ml/min in the filterability test disclosed herein.

In one embodiment, the metal base has combination of at least two of said characteristics (zeta potential, mean particle size and total surface area) inside the scope of the ranges disclosed above. If at least one of said characteristics is outside the scope of the ranges covered, typically the presence of a compound containing two or more hydroxyl groups aids filterability allowing an emulsion composition to have a filterability value of more than 8 ml/min in the filterability test disclosed herein.

In one embodiment, the present invention provides an emulsion composition comprising:

(a) a first phase comprising:

-   -   (i) an oil soluble inert medium; and     -   (ii) an emulsifier capable of forming a water-in-oil emulsion;         and

(b) a second phase comprises:

-   -   (i) a metal base;     -   (ii) an aqueous medium; and     -   (iii) optionally a compound containing two or more hydroxyl         groups,         wherein the metal base has combination of at least two of said         characteristics (zeta potential, mean particle size and total         surface area) inside the scope of the ranges disclosed above.

In one embodiment, the metal base has a nitrogen surface area below 20 m²g⁻¹ and these materials may be employed over the whole scope of the invention. Examples of a commercially available metal base include calcium hydroxide (milk of lime) available from Lhoist with a low nitrogen BET total surface area of about 2 m²g⁻¹, or about 10 m g as described in the patent application filed by ‘Lhoist Recherche& Développement’ in Belgium on 28 Jul. 2003 (filing number 2003/0426) with a PCT filing date of 27 Jul. 2004 (filing number PCT/EP2004/051609).”. Other commercial suppliers of similar calcium hydroxide materials include Omya UK Limited or Mississippi Lime Company.

In one embodiment, the presence of a compound containing two or more hydroxyl groups further aids filterability of a metal base having all said characteristics within the ranges of the disclosed herein.

In one embodiment, the metal base has a nitrogen surface area above 20 m²g⁻¹ and these materials may be employed in the presence of a compound containing two or more hydroxyl groups. Examples of a commercially available metal base include Wolfrasorp™ DSP (nitrogen BET total surface area of about 40 m²g⁻¹, commercially available from Lhoist) or Precal™72 commercially available from Schaefer.

Alternatively, a suitable calcium hydroxide may be prepared by the preparative example P-1.

P-1

1.5 kg of calcium hydroxide slurry is prepared by blending 22 wt % solid and 78 wt % of de-ionised water in a vessel. The contents of the vessel are stirred with a paddle stirrer for one hour. The slurry is then subjected to grinding step to reduce the particle size of the slurry. The grinding is carried out in a using a vertical bead mill by placing 300 g of the slurry into a grinding flask with 700 g of 4 mm glass beads (grinding media) and milling for 3 hours or until the mean particle size is below 20 μm.

Aqueous Medium

The aqueous medium includes water or another oil insoluble solvent or a blend(s) thereof. Water soluble organic materials or salts may be added to depress the freezing point of the water/solvent and/or to make the water/solvent more effective in dissolving or dispersing the base.

The water used may be taken from any source and includes tap, deionised, de-ionised to a conductivity of <30 microsiemens/cm; demineralised, purified, recycled water, gray ship water, seawater or mixtures thereof.

In one embodiment, the aqueous medium includes an oil insoluble solvent such as a monohydric alcohol containing 1 to 5 carbon atoms or a polyhydric alcohol containing 2 to 5 carbon atoms, an ether, and various other solvents that are not soluble in SAE 30 paraffinic oils to an extent of 1 g/100 ml of oil at 25° C.

Generally, the aqueous medium and metal base is in the form of a slurry. As a consequence, the total combined amount of the aqueous medium and metal base present is in one embodiment at 0.01 wt % to 40 wt %, in another embodiment at 1 wt % to 35 wt %, in another embodiment at 5 wt % to 30 wt % and in another embodiment at 10 wt % to 22 wt % of the emulsion composition.

Generally, the slurry may have a solids content of metal base in one embodiment of greater than 15 wt %, in another embodiment above 20 wt %. Examples of a range of the solids content present include 16 wt % to 40 wt % or 20 wt % to 30 wt %.

Compound Containing Two or More Hydroxyl Groups

The invention optionally includes a compound containing two or more hydroxyl groups. In one embodiment, the compound containing two or more hydroxyl groups is present.

The compound containing two or more hydroxyl groups is present in one embodiment from 0 wt % to 10 wt %, in another embodiment 0.05 wt % to 5 wt %, in another embodiment from 0.05 wt % to 4 wt % and in another embodiment from 0.1 wt % to 3 wt % of the emulsion composition.

The compound containing two or more hydroxyl groups in one embodiment contains 2 to 12 hydroxyl groups, in another embodiment 2 to 10 hydroxyl groups an in another embodiment 2 to 8 hydroxyl groups.

The compound containing two or more hydroxyl groups includes an ethylene glycol, including di-, tri- and tetraethylene glycol; a propylene glycol, including di-, tri- and tetrapropylene glycol; a glycerol; butane diol; hexane diol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose; cyclohexane diol; erythritol; and pentaerythritols, including di- and tri- pentaerythritol; or mixtures thereof. In one embodiment the compound containing two or more hydroxyl groups is ethylene glycol, diethylene glycol, triethylene glycol, glycerol, sorbitol, pentaerythritol dipentaerythritol or mixtures thereof.

Other Performance Additive

The emulsion composition optionally further includes at least one other performance additive. The other performance additive compounds include a metal deactivator, a detergent, a dispersant, an extreme pressure agent, an antiwear agent, an antioxidant, a friction modifier, a corrosion inhibitor, a foam inhibitor, a demulsifiers, a pour point depressant, a seal swelling agent or mixtures thereof. In one embodiment the emulsion composition further contains a detergent, a dispersant or mixtures thereof.

The total combined amount of the other performance additive compounds present on an oil free basis in ranges from 0 wt % to 25 wt %, in one embodiment 0.01 wt % to 20 wt %, in another embodiment 0.1 wt % to 15 wt % and in yet another embodiment 0.5 wt % to 10 wt % of the emulsion composition. Although one or more of the other performance additives may be present, it is common for the other performance additives to be present in different amounts relative to each other.

Dispersants

Optionally, the invention further comprises a dispersant. The dispersant is known and includes an ashless-type dispersant. The ashless type dispersant are characterised by a polar group attached to a relatively high molecular weight hydrocarbon chain. Typical ashless dispersants include N-substituted long chain alkenyl succinimides. Examples of N-substituted long chain alkenyl succinimides include polyisobutylene succinimide with number average molecular weight of the polyisobutylene substituent in the range 350 to 5000, in one embodiment 500 to 3000. Succinimide dispersants and their preparation are disclosed, for instance in U.S. Pat. No. 4,234,435. Succinimide dispersants are typically the imide formed from a polyamine, typically a poly(ethyleneamine).

In one embodiment, the invention further comprises at least one dispersant derived from polyisobutylene succinimide with number average molecular weight in the range 350 to 5000, in one embodiment 500 to 3000. The polyisobutylene succinimide may be used alone or in combination with other dispersants.

In one embodiment, the invention further comprises at least one dispersant derived from polyisobutylene, an amine and zinc oxide to form a polyisobutylene succinimide complex with zinc. The polyisobutylene succinimide complex with zinc may be used alone or in combination.

Another class of ashless dispersant is Mannich bases. Mannich dispersants are the reaction products of alkyl phenols with aldehydes (especially formaldehyde) and amines (especially polyalkylene polyamines). The alkyl group typically contains at least 30 carbon atoms.

The dispersants may also be post-treated by conventional methods by a reaction with any of a variety of agents. Among these are urea, thiourea, dimercaptothiadiazoles, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleic anhydride, nitriles, epoxides, boron compounds, and phosphorus compounds.

In one embodiment of the invention, the dispersant is borated using a variety of agents selected from the group consisting of the various forms of boric acid (including metaboric acid, HBO₂, orthoboric acid, H₃BO₃, and tetraboric acid, H₂B₄O₇), boric oxide, boron trioxide, and alkyl borates. In one embodiment, the borating agent is boric acid which may be used alone or in combination with other borating agents.

The borated dispersant may be prepared by blending the boron compound and the N-substituted long chain alkenyl succinimides and heating them at a suitable temperature, typically 80° C. to 250° C., in one embodiment 90° C. to 230° C. and in another embodiment 100° C. to 210° C., until the desired reaction has occurred. The molar ratio of the boron compounds to the N-substituted long chain alkenyl succinimides is typically 10:1 to 1:4, in one embodiment 4:1 to 1:3, and in another embodiment 1:2. An inert liquid may be used in performing the reaction. The liquid may include toluene, xylene, chlorobenzene, dimethylformamide and mixtures thereof.

The dispersant is present in one embodiment from 0 wt % to 10 wt %, in another embodiment 0.01 wt % to 5 wt %, in another embodiment 0.05 wt % to 3.5 wt % and in another embodiment 0.1 wt % to 3 wt % of the emulsion composition.

Detergent

The invention optionally includes a detergent. The detergent is known and includes neutral or overbased, Newtonian or non-Newtonian, basic salts of alkali, alkaline earth and transition metals with one or more hydrocarbyl sulphonic acid, salixarene (the organic substrate used to prepare a salixarate), carboxylic acid, phosphorus acid, mono- and/or di-thiophosphoric acid, alkyl phenol, sulphur coupled alkyl phenol compounds, salixarates, saligenins, sulphonates, phenates, sulphur-containing phenates or mixtures thereof. Commonly used metals include sodium, potassium, calcium, magnesium lithium or mixtures thereof. Most commonly used metals include sodium, magnesium, calcium or mixtures thereof. Detergents and in particular overbased detergents and their preparation are disclosed in U.S. Pat. No. 3,629,109.

The detergent is present in one embodiment from 0 wt % to 10 wt %, in another embodiment 0.05 wt % to 9 wt %, in another embodiment from 0.1 wt % to 8 wt %, in another embodiment 0.5 wt % to 7 wt % and in another embodiment from 1 wt % to 6 wt % of the emulsion composition.

Other performance additives such as corrosion inhibitors including octylamine octanoate, condensation products of dodecenyl succinic acid or anhydride and a fatty acid such as oleic acid with a polyamine; metal deactivators including derivatives of benzotriazoles, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles or 2-alkyldithiobenzothiazoles; foam inhibitors including copolymers of ethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate; antioxidant include a diphenylamine, a hindered phenol, a molybdenum dithiocarbamates or a sulphurised olefin; extreme pressure agents including amine or metal salts of alkyl and dialkylphosphoric acids; demulsifiers including trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides; and friction modifiers including fatty acid derivatives such as amines, esters, epoxides, fatty imidazolines, condensation products of carboxylic acids and polyalkylene-polyamines and amine salts of alkylphosphoric acids may also be used in the composition of the invention.

Process

The present invention further provides a process for preparing an emulsion composition comprising:

(1) mixing a metal base in an aqueous medium to form a slurry and optionally a compound containing two or more hydroxyl groups;

(2) adding an oil soluble inert medium to the slurry of step (1) to form an emulsion; and

(3) adding an emulsifier capable of forming a water-in-oil emulsion,

wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.

In one embodiment the invention provides a process for preparing an emulsion composition comprising:

(1) mixing a metal base in an aqueous medium to form a slurry and a compound containing two or more hydroxyl groups;

(2) adding an oil soluble inert medium to the slurry of step (1) to form an emulsion; and

(3) adding an emulsifier capable of forming a water-in-oil emulsion, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.

The temperature the process is carried out at for steps (1) to (3) in one embodiment is 15° C. to 130° C., in another embodiment 20° C. to 120° C. and in another embodiment 25° C. to 110° C. The process is carried out for a period of time in one embodiment for 30 seconds to 48 hours, in another embodiment 2 minutes to 24 hours, and in another embodiment 5 minutes to 16 hours. The process is carried out at a pressure in one embodiment of 86.4 kPa to 266 kPa (650 mm Hg to 2000 mm Hg), in another embodiment 91.8 kPa to 200 kPa (690 mm Hg to 1500 mm Hg), and in another embodiment 95.1 kPa to 133 kPa (715 mm Hg to 1000 mm Hg).

The process optionally includes mixing other performance additives as described above. The optional performance additives may be added sequentially, separately to step (2) and/or step (3). In one embodiment the process provides the emulsion composition as a concentrate.

Industrial Application

The compositions of the present invention are useful as detergents in an internal combustion engines, for example diesel fuelled engines, gasoline fuelled engines, natural gas fuelled engines or a mixed gasoline/alcohol fuelled engines.

In one embodiment of the invention provides a method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the emulsion composition as described herein. The invention is suitable for an internal combustion engines such as a 2-stroke or a 4-stroke marine diesel engine, especially a 2-stroke engine. The use of the emulsion composition in an internal combustion engine may impart one or more property from cleanliness, spreadability, corrosive wear resistance and improved filterability.

The following examples provide an illustration of the invention. These examples are non exhaustive and are not intended to limit the scope of the invention.

EXAMPLES Examples 1 to 16 and Reference Examples 1 and 2

An emulsion composition is prepared by blending a milk of lime with a solids content as shown in Table 1; 1.2 wt % of a hydrocarbyl substituted carboxylic acid acylating agent emulsifier; 0.01 wt % of an antifoam agent; 0.5 wt % of a dispersant; and 3.8 wt % of a mixture of an overbased and a neutral detergent, optionally a compound containing 2 or more hydroxyl groups present at 1 wt % or 2 wt % as shown in Table 1; and the balance of the emulsion composition is an oil of lubricating viscosity.

TABLE 1 Milk Hydroxy of Lime Hydroxy Compound Solids Example Compound (wt %) Milk of Lime Content REF 1 None — Precal 72 19.1 REF 2 None — Wolfrasorp DSP 23.8 EX 1 None — Lhoist low TSA 18.1 EX 2 Sorbitol 0.43 Lhoist low TSA 18.7 EX 3 Ethylene Glycol 1 Lhoist low TSA 19 EX 4 Ethylene Glycol 2 Lhoist low TSA 19 EX 5 Glycerol 1 Lhoist low TSA 19 EX 6 Glycerol 2 Lhoist low TSA 19 EX 7 Sorbitol 1 Lhoist low TSA 25 EX 8 Sorbitol 2 Lhoist low TSA 25 EX 9 Sorbitol 0.43 Precal 72 20.3 EX 10 Ethylene Glycol 1 Precal 72 20.3 EX 11 Ethylene Glycol 2 Precal 72 20.3 EX 12 Glycerol 1 Precal 72 20.3 EX 13 Glycerol 2 Precal 72 20.3 EX 14 Sorbitol 0.43 Wolfrasorp DSP 21.5 EX 15 None — Durcal 5 20.6 EX 16 Sorbitol 0.43 Durcal 5 22.5 EX 17 None — Lhoist* 23.6 EX 18 Sorbitol 0.43 Lhoist* 22.7 Footnote to Table 1: wt % of sorbitol is based on using a 70% aqueous solution of sorbitol; Lhoist TSA is Lhoist a milk of lime with a low nitrogen BET total surface area of about 10 m²g⁻¹; and Lhoist* is a milk of lime with a nitrogen BET total surface area of about 2 m²g⁻¹.

Reference Example 3 (REF3) is the same as Reference Example 1, except the formulation has been stored for 2 weeks. Test 1: Spreadability

The spreadability of a sample droplet was measured using a AMB310H™ moisture analyzer available from LabPlant. The experimental procedure involves placing a sample pan composed of cast iron on the moisture analyzer balance and then closing the lid before heating using a halogen lamp to 150° C. or 250° C. and holding until the temperature had equilibrated. 1 drop of sample was then dropped from 1 cm above the sample pan and droplet was allowed to spread. When the droplet stopped spreading the area covered was measured. Typically better results are obtained for samples with a higher spreading area. The results obtained were:

TABLE 2 Spreadability surface Spreadability surface Example area (cm²) at 150° C. area (cm²) at 250° C. REF 1 1.65 3.30 EX 2 1.67 2.15 EX 9 1.54 1.44

The analysis indicates the emulsion composition of the invention has improved spreadability over the reference example. As a consequence less corrosive wear is anticipated.

Test 2: Bolnes Engine Test

The Bolnes Engine Test is a turbocharged, 3 cylinder, 2 stroke, low speed marine diesel engine. The Bolnes engine test allows the simultaneous testing of three different cylinder oils over a 72 hour period. Several parameters were rated/measured in the test. The most important ones are cleanliness ratings, piston ring wear, cylinder liner wear and analyses of the cylinder drain samples. The piston ring grooves, lands and skirt and the scavenging port clogging are rated for cleanliness. The weight loss of the rings is recorded as a measure of piston ring wear. The cylinder drain samples are analysed for TBN, and ICP/AES (Inductively Coupled Plasma Atomic Emission Spectroscopy).

Examples REF1 and EX1 were run in cylinders 1 and 2 respectively and before passing into the cylinder samples were passed through a 45 micron sintered ball filter. The results obtained for REF1 and EX1 were:

TABLE 3 Engine Run Data Analysed Time (hr) EX1 REF1 Iron Content from 0 0 0 ICP 24 262 899 48 550 1226 72 689 1305 Groove and Liner 72 6.84 7.28 Average Merit Rating Linear Corrosion 72 small area large area of of trace trace to light Linear Scuffing 72 none trace Honing remaining 72 45% 20% on the linear

The analysis indicates the emulsion composition of the invention has reduced wear and improved cleanliness compared to the reference example.

Test 3: Filter Blockage

The filter blockage was determined by measuring the percentage of sample filtered and a sample flow rate using a “Total Sediment in Residual Fuel Oils and Distillate Blends Vacuum Filter Rig” available from equipment manufacturer SetaClean. The experimental procedure involved adding approximately 100 ml of the examples into a calibrated measuring cylinder. The emulsion was slowly added to the sample cup on the filtration rig and allowed to sit on the filter membrane for 30 seconds before applying a vacuum of 45 kPa. The time for the emulsion to filter completely was recorded and recalculated as a measure of millilitres per minute and the amount of emulsion filtered was recorded. Typically better results are obtained for samples with a high filtration flow rates. The results obtained were:

TABLE 4 Example Filtration Flow Rate (ml min⁻¹) REF 1 0 REF 2 4.6 EX 1 11.07 EX 2 23.62 EX 9 11.13 EX 14 13.45 EX 15 15.71 EX 16 25.75 EX 17 15.75 EX 18 21.03

The analysis indicates that the emulsion composition of the invention has good filterability and filtration flow rates compared to Reference Example 1.

Test 4: Bohlin Rheometer Test

A Bohlin rheometer sold under the trade name Gemini™ equipped with a plate-plate measuring geometry is used to determine the rheological properties of the Ca(OH)₂ suspensions during dewatering. The Ca(OH)₂ suspensions is loaded in a dewatering cell, which allows drainage of the suspension by applying a vacuum to a porous bottom plate. A pressure difference of 60 kPa is used for all measurements to obtain reproducible dewatering conditions. The elastic or storage modulus G′ of each Ca(OH)₂ suspension is recorded versus time. The upper plate of the measuring geometry is kept in contact with the sample surface during the entire course of the measurement. The results presented in Table 5 were based on an average of three measurements. Generally better results are obtained for samples with a longer period of time before the formation of a filter cake.

TABLE 5 Time of formation of filter cake as measured by Example rheology/dewatering technique (seconds) REF 1 55 EX 1 65 EX 9 85 EX 2 100

The results indicate that the metal base of the invention is less susceptible to formation of a filter cake.

In summary the emulsion composition has at least one property from cleanliness, spreadability, corrosive wear resistance and improved filterability.

While the invention has been explained, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements. As used herein, the expression “consisting essentially of” permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration. As used herein any member of a genus (or list) may be excluded from the claims. 

1. An emulsion composition comprising: (a) a first phase comprising: (i) an oil soluble inert medium; and (ii) an emulsifier capable of forming a water-in-oil emulsion; and (b) a second phase comprises: (i) a metal base; (ii) an aqueous medium; and (iii) optionally a compound containing two or more hydroxyl groups, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.
 2. The emulsion composition of claim 1, wherein the oil soluble inert medium is an oil of lubricating viscosity.
 3. The emulsion composition of claim 3, wherein the oil of lubricating viscosity has a SAE grade of 30-50.
 4. The emulsion composition of claim 1, wherein the emulsifier is a hydrocarbon lubricant-soluble hydrocarbyl substituted carboxylic acid acylating agent.
 5. The emulsion composition of claim 4, wherein the emulsifier is a hydrocarbyl-substituted succinic acid or anhydride.
 6. The emulsion composition of claim 1, wherein the emulsifier has a HLB of 1 to
 8. 7. The emulsion composition of claim 1, wherein the metal base has a total surface area of 2 m²g⁻¹ to 10 m²g⁻¹.
 8. The emulsion composition of claim 1, wherein the metal of the metal base is calcium.
 9. The emulsion composition of claim 1, wherein the metal base is a calcium oxide or hydroxide.
 10. The emulsion composition of claim 1 further comprising the compound containing two or more hydroxyl groups.
 11. The emulsion composition of claim 10, wherein the compound containing two or more hydroxyl groups has 2 to 8 hydroxyl groups.
 12. The emulsion composition of claim 11, wherein the compound containing two or more hydroxyl groups is ethylene glycol, diethylene glycol, triethylene glycol, glycerol, sorbitol, pentaerythritol, dipentaerythritol or mixtures thereof.
 13. The emulsion composition of claim 1 further comprising a detergent, a dispersant or mixtures thereof.
 14. An emulsion composition comprising: (a) a first phase comprising: (i) 50 wt % to 97 wt % of an oil soluble inert medium; and (ii) 0.05 wt % to 10 wt % of an emulsifier capable of forming a water-in-oil emulsion; and (b) a second phase comprises: (i) a metal base; (ii) an aqueous medium; (iii) 0.05 wt % to 5 wt % of a compound containing two or more hydroxyl groups; and (iv) 0.5 wt % to 10 wt % of at least one other performance additive, wherein a base in the form of an alkali metal or an alkaline earth metal oxide, hydroxide, carbonate, bicarbonate; or combinations thereof; and wherein the emulsion composition has a flow rate through a 45 μm filter of more than 8 ml/min in a filterability test carried out at ambient temperature and 45 kPa applied vacuum; wherein the filter has diameter of 5 cm and a mesh size of about 45 μm; and wherein the oil soluble inert medium in the filtration test is an oil of lubricating viscosity of a SAE 50 base oil.
 15. A method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the emulsion composition of claim
 1. 16. The method of claim 15, wherein the internal combustion engine is a 2-stroke or a 4-stroke marine diesel engine. 